In these years, diligent studies have been carried out on a light emitting device in which a semiconductor light emitting element (solid-state light source) such as a light emitting diode (LED) or a laser diode (LD) is used as an excitation light source.
As an example of such a conventional light emitting device, Patent Literature 1 discloses a technique in which a single optical fiber is used.
According to the technique disclosed in Patent Literature 1, a normal optical fiber is used as a light guide member. Accordingly, the optical fiber naturally has a light incidence section and a light exit section which have identical cross-sectional areas.
On the other hand, as another examples of the conventional light emitting device, Patent Literatures 2 and 3 disclose techniques in which a bundle fiber made up of a plurality of bundled optical fibers is used.
According to the technique disclosed in Patent Literatures 2 and 3, a plurality of excitation light sources emit rays of light which are bundled with the use of the bundle fiber so as to generate high-power light.
Note that the techniques disclosed in Patent Literatures 2 and 3 are different from that of Patent Literature 1 in that a plurality of optical fibers are used in the technique disclosed in Patent Literatures 2 and 3. However, the bundle fiber is made up of a plurality of bundled optical fibers as described above. Accordingly, in general, the bundle fiber has a light incidence section and a light exit section which have identical cross-sectional areas as disclosed in Patent Literature 2.
Note that, according to the technique disclosed in Patent Literature 3, a light exit section has a cross-sectional area which is larger than that of a light incidence section. However, rays of light emitted from an emission edge of the bundle fiber are converged with the use of a convex lens, and thereby a problem is solved that the light exit section has the cross-sectional area larger than that of the light incidence section.